Project Summary The goal of the Behavioral Science Core (BSC) is to support the ERC-CFAR mission by facilitating the development and implementation of interdisciplinary, theory-driven, rigorous behavioral and social science research that aligns bench, bedside and community to prevent new HIV infections and improve HIV care. Behavioral and social science research continues to be indispensable to attenuating the HIV/AIDS epidemic, through ?combination prevention? which joins behavioral, social, and biomedical approaches; understanding acceptability, uptake, and adherence to effective biomedical technologies such as condoms, topical microbicides, intravaginal rings, PEP and PrEP, and emerging therapies such as bNAb; and reducing attrition at each stage of the HIV Prevention and Care continuum. The BSC has five Specific Aims: 1. Support development of new, innovative behavioral research by providing technical assistance on study design; qualitative and mixed methods through a new Qualitative Method Resource; and measurement. With the Clinical Translational Implementation Science Core (CTIS), we will assure translational potential. 2. Provide access to the Cognitive Interview Lab, a new resource staffed by trained interviewers who can test new measures and evaluate whether existing measures fit new populations or purposes. 3. Lead the ERC-CFAR Community Participatory Partnership to shape the ERC-CFAR research agenda. 4. With the Biomarker and Advanced Technology Core (BATC), guide combination measurement by developing new, and advising on existing, biomarkers for behavioral outcomes including ART and PrEP adherence from blood and hair drug anabolite assays, and RSID (a measure of semenogelin) in vaginal swabs and SPERM HI-LITER (immunofluorescence assay that detects sperm) for rectal swabs. 5. With the Development Core, mentor ESI, community and clinical researchers in behavioral research methods and community collaboration, and support collaboration through CFAR catalytic microgrants. The strengths of the BSC ? its foundation in existing expertise at Einstein and Hunter and its infrastructure (Qualitative Methods Resource, Cognitive Interview Lab, Biomarker advice, CPP) -- will provide essential support to enhance the capacity of the ERH-CFAR to meet its agenda, to arrest the AIDS epidemic.